So unless I missed something, your math is way off. I counted 138 different pieces of story. Any of them can occur at any time, so there are 138^5 possible playthroughs, or 50,049,003,168. If you make sure not to read the same piece more than once in a given playthrough, that's 138x137x136x135x134, or a measly 46,513,297,440.
And they're all interesting.